Baby pigs are born in particularly weak and defenseless condition. Their skin and hair are thin and fragile, compared to the young of other economic animals, and their reserves of stored nutrients are very low. In particular, the fat reserves of a piglet are very slight.
Thus, piglets deplete their glycogen reserves very soon after birth. If an individual piglet is slow to suckle or gets less than its share of colostrum and milk, it will very soon be in desperate condition. The observed result is that only about 75% of piglets survive to adulthood.
It has been found that the survival of piglets can be measurably improved by expedients which raise the fat content of sows' colostrum and milk. For example, Moser and Lewis reported in Feedstuffs, Mar. 3, 1980, that the addition of fats to the diet of lactating sows increased the fat content of their colostrum and milk, and resulted in an increase of about 2.6% in the survival of their piglets, compared to normally-fed controls.
The addition of fats to animal feeds, however, is rather difficult. The physical mixing involved is much more difficult than the simple mixing of grain and cereal products involved in ordinary feeds, and the resulting fat-containing feed is difficult to measure, transport and store. The amounts of fat necessary to produce the desired effect add appreciably to the cost of sows' feed, as well. Until now, there has been no physiological way to increase fat content of sows' colostrum and milk.
The present invention provides a method of increasing the fat concentration of sows' colostrum and milk, by administering one of a small group of phenethanolamines. The phenethanolamines constitute a very large and complex group of pharmaceuticals, useful in both human and veterinary medicine. Various members of the broad class of phenethanolamines have many diverse activities, and accordingly can be used for a number of pharmacological purposes.
For example, European patent publication No. 0117647, of Anderson et al., teaches that a group of phenethanolamines, including some of those used in the present invention, can be effectively administered to animals to improve feed efficiency and carcass quality. The patent mention pigs as a preferred animal, and states that use of its compounds causes the treated animal to be lean, as compared to untreated animals. U.S. Pat. Nos. 4,407,819 and 4,432,995, of Kiernan et al., teach that other compounds used in the present invention increase lean meat deposition and the lean to fat ratio, as well as feed efficiency and growth rate, in animals, including swine.
It has been established that the only lipid fraction of blood which is taken up in significant and consistent quantity by the sow's mammary gland is the triglyceride fraction. Lactation, Larsen and Smith, Eds., Vol. II, p. 26 (Academic Press, 1974).
Some phenethanolamines have been shown in the past to release fat deposits in the body, in the form of free fatty acids. For example, the above-mentioned European patent application states at page 31 that its compounds, when administered to normal swine, increased the concentration of non-esterified fatty acids in the blood, compared to untreated control animals.
Another class of phenethanolamines, which are specified extremely precisely in terms of their stereochemistry, is taught by U.S. Pat. No. 4,391,826, of Mills et al. These compounds are said to be useful as anti-obesity agents. The patent shows at the top of column 13 that administration of typical compounds to rats caused a great increase in the concentration of free fatty acids in the blood.